Gear pump



Aug- 22, 1961 w. c. TRAUTMAN 2,996,999

GEAR PUMP Filed Jan. 22, 1958 6 Sheets-Sheet 1 www@ ATTORNEYS Aug- 22, 1961 w. c. TRAUTMAN 2,996,999

GEAR'PUMP Filed Jan. 22, 1958 6 Sheets-Sheet 2 l i@ (Q, 5 A 46 34 BY www ATTORNEYS Aug. 22, 1961 w. c. TRAUTMAN 2,996,999

GEAR PUMP Filed Jan. 22, 1958 6 Sheets-Sheet 5 INVENTOR BY fai/ga@ ATTORNEYS Aug- 22, 1961 w. c. TRAUTMAN 2,996,999

GEARPUMP Filed Jan. 22, 1958 ATTORNEYS Aug- 22, 1961 w. c. TRAUTMAN 2,996,999

GEARPUMP Filed Jan. 22, 1958 6 Sheets-Sheet 5 v/Qg INVENTOR Mme aaf/mw BY f?? ,m

Aug. 22, 1951 w. c. TRAUTMAN GEAR PUMP Filed Jan. 22, 1958 6 Sheets-Sheet 6 ATTORNEY` nited States Patent 2,996,999 GEAR PUMP Walter C. Trautman, Chicago, Ill., assignor to Hupp Corporation, Cleveland, Ohio, a corporation of Virginia Filed Jan. 22, 1958, Ser. No. '710,532 z Claims. (Cl. 10s- 126) This invention relates to gear pumps and more particularly to self-compensating gear-tooth pumps providing optimum clearance between relatively moving surfaces of pumping components.

Gear tooth pumps of previously known conventional construction consists of a combination of gears, casings and end plates, and the production of, and structural cooperation between, these components in the combination must be very closely controlled as a necessary and vital factor for satisfactory pump operation. In the simplest form of conventional gear tooth pumps, the casing and gears have relatively minute critical ixed clearances between gear peripheries and surrounding casing walls and between gear tooth side faces and the casing end plates and depend upon these relatively minute clearances for the pumping seals. As a consequencethe pumps have large, relatively moving areas separated by such relatively minute clearances which usually results in considerable friction losses, leakage losses and hence in low mechanical eiciency.

Possibly the greatest limiting factor on the output pressure capacity of gear tooth pumps is the high load imposed on the gear shaft bearings by large unbalanced hydraulic pressures between outlet and inlet sides. In a conventional gear tooth pump, the inlet portion of the combination pump structure encompasses only a small extent of the gear peripheries and the area of casing periphery between the high pressure outlet side of the meshing gears and the low pressure inlet side of the gears is subject to varying magnitudes of outlet pressure. Because of the small critical clearances between gears and casing the pressure of duid in those clearance spaces decreases in a progressive manner around the peripheries of the gears from the pump outlet to a position closely adjacent to the inlet portion of the gear peripheries Because there is a small leakage through the peripheral clearance space, the fluid seal thus obtained cannot be .absolute and this factor accounts for a pressure gradient around the gears. Considerable hydraulic pressure difference is thus applied against a major lpercentage of the lgear perpheries resulting in a correspondingly high bearing load on the gear shaft bearings. A further disadvantage directly related to the gradient nature of this high pressure loading on the two gears in a conventional pump is that the p-ressure forces on each gear approach a `condition approximating a balanced couple about the gear axis which makes such a pump mechanism highly inefficient and even inoperative if it is desired to be used as a motor.

As discussed above, the basic principle of operation of simple gear tooth pumps requires close control of the critical gear to casing clearance, and high bearing loads are inherent. These two factors contribute to cumulative rapid self-destruction of Asuch pumps because even a minute gear shaft bearing wear will enable an increase in gear periphery clearance adjacent the gear periphery portions subject to outlet pressure. This increase multiplies bearing loads because of increased magnitudes in the pressure gradient along the critical clearance peripheral seal area and in turn causes `faster bearing wear. As this rapid self-destruction progresses and gear teeth eventually hit and wear directly on the peripheral casing wall adjacent the inlet. This action can freeze the pump gears or further increase peripheral clearances "ice closer to the outlet. At this stage the pump becomes useless. Y

Previously known geartooth pumps require at least some portion of casing structure as a requisite part of the pumping mechanism seal, i.e. there must be some type of direct relative cooperation between an enclosing casing and the pumping gears to provide the required pumping and high pressure sealing action. A resulting effect of such structure is to subject the casing to high hydraulic pressures over a large portion of its interior, particularly on areas of the casing end plates. Consequently the end plates must be of heavy, thick-Walled construction and the bolts, or the like, which connect the end plates to the casing must be of suicient strength to withstand the deh veloped forces. This requirement results in a high unit weight with a proportionate amount of material for construction. Reduction of this high weight and the use of less material are highly advantageous economical production and service features both of which are realized by this invention as will become apparent.

Accordingly, a primary object of yhis invention resides in the p-rovision of a novel gear-tooth pump with selfcompensating pumping mechanism supported in a casing structure which serves primarily as support structure for the pumping mechanism, and hence can be produced without the necessity of machining critical pumping surface dimensions.

A further object resides in the provision of a novel gear-tooth pump in which the pump gears and the casing are formed with optimum non-critical clearance-s and a pressure discharge assembly cooperates with a minimum extent of the gears adjacent the discharge side of intermeshed teeth whereby a major portion of the pump gear teeth are in contact with and directly receptive to the incoming fluid at the pump inlet, enabling the pump to be rotated at very high operational speeds and still accomplishing complete lilling of the pump gear teeth before they move into pumping cooperation with the discharge assembly.

A still further object is to provide a self-compensating gear pump with an independent pumping assembly incorporating a pressure actuated gear Atooth sealing member in combination with two independent gear side surface sealing members, all of said gear sealing members being urged into sealing engagement with the gears by hydraulic pressure equal to the pump discharge pressure at the meshing gear teeth output zone.

Another object resides in the provision of a novel gear tooth pump which has a casing type support for intermeshing pumping gears with non-critical clearances between the casing support structure and the gear end faces and peripheries, a thrust block engaging a minimum portion of the gear peripheries and two seal plates overlapping the gear end faces and the thrust block and sealingly biased between the casing Wall into overlapped engagement with the gear end faces and the thrust block.

A related further object is to provide the seal plates, which sealingly engage portions of the side faces of the gea-r teeth and the thrust block and seal a space between thrust block and intermeshed gear teeth in uid communication with the pressure discharge side of the pump gears, with structure disposed between each seal plate and the casing to resiliently maintain the seal plate against the gears and thrust block.

A still further object resides :in the provision of a novel self-compensating gear tooth pump including a support structure which journals the pumping gears in meshed relation, a thrust block contoured to fit a portion of the peripheries of both pumping gears having a thickness equal to the thickness of the pumping gears and having a discharge passage extending through the thrust block between the inner and outer pressure faces of the 3 block, the thrust block being Amaintained by a biasing force in sealing engagement with the gears. In conjunction with this object, a further object resides in the provsion l`of a pressure area on the outletside of the thrust block pressure passage of suciently greater dimension 'than the veffective area of fthe vthrust block pressure face 'and subjected t'o outlet pressureto provide a Controlled biasing force on the thrust block.

Another object resides in 'a novel self-'compensated A`gear tooth pump, as in the preceding `object, which includes t-wo seal plates overlappingthe sides 'of'said tirust block and the end faces of the teeth intermeshed gears Aadjacent their discharge to 'completely cover the pressure discharge space between the intermeshed gears 'and said thrust block, and resilient seal 'rings cooperate between the seal plates and the support structure to bias the seal plates toward 'engagement with the thrust block and pumping gears. In relation to this object, a rfurtherobject resides in the novel provision forpassage of iiuid under pressure to a pressure area on said seal plate defined by the sealing ring so output pump pressure can be utilized to bias the seal plates toward the thrust block and pumping gears and the biasing force will be Vautomatically compensated for changes in pump output pressures.

Still another object resides in providing 'a gear tooth pump with a novel, full oating, disohargezone, sealing assembly which includes A a thrustblock unit consisting Yof two halvessubjected to a fluid pressure differential biasing force tending to maintain the lhalves in fluid lilm rsealed engagement with the gear teeth Vand 'in direct sealed engagement with the pump body.

Yet another object -resides in providing a gear 'tooth pump with Va novel, full floating, discharge zone, sealing assembly which includes a thrust block funit made of flexible material and provided with an integral, block to casing, annular pressure sealing lip and tapered wall portions subjected to a differential biasing force resulting in wall deection toward a discharge pressure controlled fluid lilm sealing cooperation with the pumping gear peripheries.

It is a still further related objectto provide the 'seal plates with an orifice type fluid communication 'to the pump pressure space yand to provide Va controlled fluid youtlet from the seal plates sealed area selectively operable to 'relieve fluid pressure from within the seal plate sealed areas thus enabling the vsealtplates to be biased by -pump 2,996,999 Y' 'Y e discharge pressure out of operative engagement with the thrust block and pumping ,gears to cause immediate ccssation of pumping output.

Further novel features and other objects of this inven- -tion will become apparent from the following detailed description, discussion and the appended claims taken in conjunction with lthe accompanying drawings showing preferred structures and embodiments in which:

FIGURE 1 is a side elevation of a self-compensating optimum clearance -gear tooth pump constructed -in -aecordance with this invention, one of the casing end plates being omitted to show interior details;

FIGURE 2V is a section, taken on line 2-2 of FIGURE l, showing both end plates and illustrating the various 'seal devices;

FIGURE 3 is a section taken on line 3-3-of FIGURE 1 and illustrates the thrust block, seal plates and seal devicesg V FIGURE 4 is a pictorial perspective of `a preferred type of gear tooth pump illustrating principles of this invention;

FIGURE 5 is a side elevation of a conventional, fixed clearance, gear tooth pump, with one `of the-casing end plates omitted to enable comparison with FIGUREl;

FIGURE 6 is a horizontalsection,.takenonrline 6-6 of FIGURE 5 showing inlet and'outlet of the conventional gear tooth pump;

u lFIGURE 7 isla detail view of the -pump structure in FIGURES 1-4 showing a portion of the thrust block and one of the gears illustrating the extent of desired gear tooth engagement;

FIGURE 8 is a schematic view illustrating the ability of the self compensating pump of this invention to operate without an enclosing casing;

FIGURE 9 is a vertical 'section taken on line 9 9 of FIGURE 2 and illustrates further details and pressure areas of the thrustblock and pressure loaded gear teeth;

FIGURE 10 is a partially broken away and expanded perspective view showing the relationship of the thrust block and seal plates and a part of the pump casing;

FIGURE l-l .is a detail section illustrating a modified thrust block;

FIGURE 12 is a detail section illustrating a lirst alternate form of double thrust block assembly;

FIGURE 13 is `a `schematic hydraulic system for a press illustrating a modilication `enabling controlled relief of pumping pressure;

FIGURE 14 is a detail view illustrating the orifice located in the seal plates of the FIGURE Y13 embodiment, in lieu of ordinary pressure passages;

FIGURE 15 is a :theoretical curve illustrating the theory of liquid film thickness relationship to unit pressures applied von the liquid film;

lFIGURE 16 is aside elevation of 'a pump in accord with this invention, having alsecond alternate form of 'a iioating pressure seal assembly utilizing a split thrust block without an area seal;

FIGURE 17 is a section view taken essentially on line 17-17 of FIGURE 16, the seal plate resilient seals being omitted for clarity;

FIGURE 18 is an enlarged representative section view through a half thrust block and a gear of the embodiment in FIGURE 16 to illustrate the contour of and resultant forces on the half block;

FIGURE 19 is a side elevation of still another pump in accord with this invention having a third alternate form of floating pressure seal assembly utilizing a combination thrust block and area seal; and

FIGURE 20 is 'a detail section view taken on line 2- 20 of FIGURE 19 illustrating the shape of the thrust block.

All of the iigures, withthe exception of AFIGURES 5 and 6, refer to inventive features and concepts of this invention as applied to various modifications of self-compensating pumps, FIGURES 5 and 6 represent a conventional, prior art, Viixed clearance, gear tooth pump yand are included in this disclosure as an aid in explaining the various uid forces and the manner of structural cooperation between pump components in such prior art pumps which s considered detrimental to pump life under extensive high pressure service, thus affording a background understanding-of the problems preceding the present invention andtheimprovement it contributes.

With reference to FIGURES 5 and 6, the primary components of a fixed clearance pump 20, in simplied form, are the casing 22 which includes recesses 24 and 26 receiving a pair ofiutermeshing spur gears 28 and 30, an inlet passage 32 and an outlet passage 34. The casing side surfaces 36 and 38,`particularly immediately adjacent the periphery of the gear recesses 24 and 26, are of planar shape and disposed parallel `to each other. Gears 28 and l30 can be madeintegral with their shafts 4i) and 42 or separable and non-rotatably splined or keyed to the shaft. One of the shafts (not shown) extends at one of its ends a greater distance than the other shafts and has formed on that end some means for enabling a drive connection.

As such a drive connection forms noy part of the discussion relative to the pumping operation of conventional fixed clearance gear pumps there is no need for illustration.

Two end plates 44 and 46 are secured to opposite sides of casing 22 by bolts 48 threaded into the casing 22. Both of end plates 44 and46 include a flat planar inner surface, 50 and 52 respectively. When the end plates 44 and 46 are secured to casing 22, a conlined pumping chamber is formed with the aforementioned recesses 24 and 26, the inlet 32 and the outlet 34. Boss portions 54 and 56 on respective end plates 44 and 46 include bores 58 for journalling the shafts 40 and 42 of the spur gears. The lbores 58 in one of the end plates 44 are both blind bores whereas only one of the bores 60 in end plate 46 is a blind bore, the other -bore in end plate 46 (not shown) being a through bore and including a suitable shaft seal to create a fluid seal around the projected drive connection end of gear shaft 40.

Typical radial and axial clearances required between the gears 28 and 30, the casing 22 and the end plates 44 and 46 of such a fixed clearance gear tooth pump are illustrated to an exaggerated extent for clarity. Actually the clearance between the gear periphery and adjacent wall of the casing is somewhere in the order of 0.003 to 0.004 inch and the axial clearance between the `side face of the gear and matching inner face o-f the end plates 44 and 46 is in the order of 0.0005 to 0.0010 inch.

Inlet fluid entering through casing inlet 32 contacts the intermeshed gears in the small triangular space between the intermeshed gears and casing inner w-all boundaries A and A seen in FIGURE 5. In this relatively small inlet chamber, the hollow spaces between each gear tooth must become filled with fluid as the teeth progress by rotation into sealing engagement with the circumferential inner wall of the casing recesses. The aforementioned small critical clearance must exist between the gears and the casing from boundary lines A around to the outlet space on the opposite sides of the intermeshing gears which space is in iluid communication with casing outlet 34. The radial clearance between gears and casing although very minute is still a clearance and therefore can pass a considerable volume of fluid from the pressure side to the inlet side. Because of the minute clearance there is a resultant boundary layer friction between the layer of uid in the clearance, the casing surface and the gear teeth end faces which, because it extends a major portion ofthe peripheral extent of the gears, results in an eifective although not an absolute fluid seal. This is a progressive seal resulting in a pressure gradient developed from a maximum at the discharge area back to the points A `adjacent the inlet port. In FIGURE 5 this pressure gradient is illustrated by the phantom lines B and the variation in pressures are indicated by the double headed, radial directed arrows placed within the pressure gradient diagram. The large arrows C represent the direction of ,resultant force acting on the gear shaft bearings as a result of the hydraulic pressure gradient.

Because the hydraulic pressure forces, even though reduced at locations near the inlet, exist substantially entirely around the periphery of the gears, the moment couple about the axis of each gear is relatively small considering the magnitude of pressure at the outlet port. It is this factor that makes such a fixed clearance gear type pump inefficient and in some respects inoperable as a fluid motor. Furthermore it can be seen that because of the large extent of the gear periphery which is subjected to the hydraulic pressure gradient that a high unbalanced force is created on the gear bearings which will tend to increase wear and shorten the bearing life which in turn cumulatively destroys the closely critical minute clearances surrounding the gear teeth and upon which depends the peripheral iluid sealing action for relatively efficient pump operation.

Still referring to FIGURES 5 and 6, it can readily be shown that at least 22 critical dimensions are present and must be considered during production of a fixed clearance, lgear type pump. To properly position the end plates 44 and 46 on casing 22, dowel pins are accurately located in each end plate and match with corresponding `dowel holes 62 and 64 in the matched surfaces of the casing 22. Each of end plates 44 and 46 has at least .'Seven critical dimensions which are listed below accompanied by a representative critical tolerance applicable to a gear pump approximately the size illustrated in the drawings.

(1) 'Ihe dowel pin location hole to the shaft bearing axis of one shaft bore 58 (.0005 inch). s

(2) Axis of shaft bearing bore to the axis of the adjacent'shaft bearing bore (.0005 inch).

(3) The axis of the adjacent shaft bearing bore to the opposite dowel pin location hole (.0005 inch).

(4) The first shaft Ibearing Ibore diameter (.0005).

(5) The second shaft bearing bore diameter (.0005).

(6) Offset (the side tolerance) of shaft bearing axis to the adjacent dowel pin axis (.001).

(7) Oiset (side tolerance) of the other shaft bearing bore diameter to the opposite dowel pin axis (.001).

Note-Since each end plate has the same critical dimensions, the two end plates in conjunction require at least 14 critical dimensions.

The critical dimensions of casing 22 are:

(l) The dowel pin locating hole axis to the center of the adjacent gear cavity (.0005 inch).

(2) The center of one gear cavity to the center of the adjacent gear cavity (.0006 inch).

(3) 'I'he dimension from the center of the second gear cavity to the center of the second dowel pin (.0006 inch).

(4) The radius of one gear cavity (.0005 inch).

(5) The radius of the other gear cavity (.0005 inch).

(6) The offset (side tolerance) from gear cavity center to the center of the adjacent dowel pin hole (.001 inch).

(7) The offset (side tolerance) of the other gear cavity center to the axis of the adjacent dowel pin hole (.001 inch).

(8) The thickness of the gear casing which must be machined (.001).

The foregoing dimensions do not include any dimensions of the gear perimeters, thicknesses and shaft diarneters which occur in all gear tooth type pumps. The tolerances listed above are total allowances and not plus and minus tolerances. They have been taken from a typical, commercial, fixed clearance gear tooth pump and illustrate the degree of precision required in this type of a pump.

The criticality of end plate dimensions numbers 6 and 7 above and the casing dimensions number l through 7 above have been eliminated by the present invention, as will be more fully described hereinafter, thereby reducing the above twenty-two critical dimensions in casing and end plates to eleven and constituting a major saving in production and inspection time.

Returning to FIGURES 1, 2 and 3, an exemplary embodiment of a gear pump according to the present invention is illustrated. FIGURE 9 is a vertical crosssection showing further details of inner components while FIGURE 4 is a somewhat schematic perspective view which illustrates basic components of a pump incorporating the inventive concepts of this invention.

The major components of pump 80, FIGURE 1, are pump gears 82 and 84, a thrust block 86, seal plates 88 and 90, an annular thrust block seal 92 and upper and lower seal plate resilient seals 94 and 96. These eight components are assembled in a relatively loose abutting relationship within a support casing 98 which surrounds the gears with relatively large non-critical clearances. End plates 102 and 104 have bores l0-6 and 108 which receive bearing sleeves 110 and 1112 for rotatably journalling gear shafts 114 and 116. One of the bores extends through its end plate and permits the projected end of one gear shaft to extend to the exterior of the gear support structure, for example, as shown in FIGURE 13. Surrounding this extended portion of one of the shafts is a seal such as the Oring 118 (FIGURE 13) to prevent fluid leakage between the shaft and the end plate bore. Any appropriate seal may be utilized at this position, and it is noted that such seal is not subjected to the high outlet pressure of the pump.

Each gear 82 and 84 may be formed integral with or keyed to its associated shaft in the manner illustrated in FIGURE 9. The form of -gear teeth used in conjunction with this invention can be any of the known types, two examples being involute or elliptical gear tooth forms such as represented in FIGURES 7 and 8 or the elliptical Davis type gear tooth described in U.S. Patent No. 2,261i143 and represented by the helical gears Vshown in FIGURE 4. Preferably the Davis type gear tooth is desired although the inherent drive weakness of the elliptical form of gear tooth will necessitate the use of helically disposed teeth. When using such teeth with the present invention the lead from one end face of one tooth to the opposite end face of the same tooth is at least equal to the distance from one tooth to the next tooth.

In FIGURE 4, only the primary components of the present pump are illustrated, these being the two gears 82 and 84, the thrust block 86 and the seal plates S8 and 90. The three resilient seal devices are emitted in this perspective View and the support structure for such components is represented by a circular casing 98 which also provides support for the bearings 118. FIG- URES 4 and 8 serve to illustrate that no external gear casing is required to enable pumping operation of this type of gear pump. The wide clearance between the gear peripheries and the supporting casing enables inlet fluid to surround and fill the spaces between gear teeth along a major portion of both gears, and minimizes the occurrence of cavitation upon high speed rotation of the gears in a conventional pump due to the maximum limits of time and force available to propel the incoming liquid into the gear-tooth cavity, as the teeth move through the inlet chamber.

The force (pressure) is determined largely by the available suction pressure (29.92 inches Hg max.) and usually not over inches in actual practice.

The time is `determined by the rotary speed of the pump and is the time which it takes one tooth-cavity to cross the inlet port.

Since all hydraulic iluids are viscous it follows that; for a given viscosity of liquid and with the force available limited by physical laws, there is a maximum time element which can be tolerated to insure complete filling (i.e. non-eavitation) of the gear-tooth cavity.

In a conventional pump the arcuate distance (and therefore time) during which filling can take place is about 60 degrees of shaft rotation. In the pump of this invention this arcuate distance is somewhere in the vi- 'cinity of 200 degrees or more.

The thrust block 86 has a Width (FIGURE 2) which must 'be exactly the same as the side face Width of the pump gears 82 and 84. This dimension is critical and must be accurately maintained. Thrust block 86 is formed to coact with the teeth end faces of both gears 82 and 84 immediately adjacent the discharge space Where the two Ygears intermesh. Two arcuate surfaces 120 and 122 at opposite ends of the pressure face of the thrust block 86 are accurately formed to the same radius as the outside or addendum circle of the pump gears 82 and 84. A pressure face 124 on thrust block 86 (FIGURE 9) is provided between arcuate surfaces 120 and 122 facing the meshing position of gears S2 and 84 and, with the gears, forms a pressure discharge zone 126 which has an essentially triangular cross-sectional shape. The length of arcuate surfaces `128 and 122 (see FIGURE 7) is such as to always engage the teeth lands along the full extent of at least one circular-pitch with straight teeth, and at least two circular-patch with teeth of helical formation where the distance from one side to the other or" a single tooth is equal to the circular pitch `distance between two gear teeth. FIGURE 7 illustrates the arcuate surface 120 of slightly greater length than is necessary for the aforementioned straight teeth of involute form.

Some means must be 'provided for maintaining 'the arcuate surfaces v and y'122 of thrust block 86 in close, approximately engaged proximity with the peripheries of the pump gears 82 and 84 and it is preferred that this force be accurately controlled, for reasons which will become apparent hereinafter.

As will be apparent from the structural arrangement disclosed in FIGURES 1, `2 and 9, the rear face V'128 of thrust block 86 will be subject to fluid under dis'- charge pressure which flows from the front face 124 through a passage 129 in thrust block 86 and, by control of the areas of portions of arcuate surfaces 12) and 122 and front face 124 and of rear face 128 which are subjected to discharge pressures, a differential pressure will be realized on the thrust block 86 which will tend to force it toward the gear peripheries with a pressure of desired magnitude relative to the magnitude of output pressure.

Seal plates 88 and 90, best shown in FIGURES 1, 2 'and 3, are illustrated as having a contour permitting the seal plate t'o contact side areas of the gears 82 and 84 within the root circles of the teeth, overlap the dead center position of intermeshed gear teeth, and engage a major portion of the side faces 130 and 132 of thrust block 86 providing a secondary wear-plate function. The contacting 'surfaces of seal plates 88 and 90 are machined smooth to closely cooperate with the coextensive side faces of the gears and of the thrust block. Each seal plate must overlie the point of gear meshing which is indicated as point G in FIGURE l. It will also overlie the extreme ends H of the arcuate surfaces of thrust block 86. It can overlie the full area of the thrust block and extend 'past the thrust block area exposed to the annular seal 92. A pressure equalizing passage 134 extends through each seal plate to permit fluid communication of pump discharge pressure from the inner to outer side of the seal plate and enables such discharge pressure to act on the outer face of the seal plates 88 and 90. Although the seal plates 88 and 90 are illustrated in FIGURES l, 2 and 3 as overlying a portion of the support casing 98 immediately adjacent the casing discharge outlet 136, such feature is not necessary although if such structure is not used, the annular seal 92 must provide a seal between the thrust block 86, the casing support structure 98 and the end plates 102 and 104, e.g. as shown in FIGURE 13.

The annular seal 92, preferably made of resilient --material such as an oil-resistant synthetic rubber (e.g. Buna N) or a corrosive resistant synthetic (e.g. Teflon), provides a fluid seal fbetween the thrust block 86, seal plates 88 and 90 and casing structure 98, as above described, and furthermore provides a resilient biasing force which tends to maintain thrust block 86 against the gear peripheries when pump 80 is not delivering fluid under pressure. Fluid under pressure acting on the internal groove 137 of annular seal 92 tends to expand seal 92, :riding its seal function and exerting a force on the thrust block 86.

An alternative possible seal construction which does not require the annular seal 92 is shown in FIGURE 11 where an integral spigot projection 140, provided on thrust block 86', extends into a cylindrical bore 142 coextensive with the support structure outlet 136'. Suitable sealing means such as the O-ring 144 disposed in an annular groove in spigot member 140 provides a fluid seal between the spigot and casing 92' preventing high pressure fiuid from flowing back to and around the rear face of the thrust block and interior of the casing structure. The relationships of the cross-sectional area of spigot member 140 and the combined effective pressure area of flat surface 124 and varying pressure areas existing on the arcuate surfaces 120' and 122 can be designed to give a differential pressure having values of desirable magnitudes necessary to force the thrust block 86' toward vthe gear peripheries, without destroying the Huid .film between teeth ends and the thrust block surfaces 120 and 122.

The discharge pressure passage 129 (FIGURES 2 and 9) provided through the thrust block 86 extends from pressure face 124 to outlet face 128. The inlet opening of passage 129 can extend substantially the entire width of the thrust block 86 and constitutes an elongated slot like aperture 127. Passage 129 is shaped to form a transition of approximately constant cross-sectional area from the inlet slot to a centrally located circular outlet 131 at the rear face of the thrust block 86. The fluid under pressure leaving thrust block 86 has a flow path substantially coextensive with the pump casing outlet 136.

Referring to FIGURE l, the support casing 98 has a gear cavity 146, providing substantial clearance around the intermeshed gears `82 and 84, and an inlet passage `148 which communicates through the casing wall to the cavity 1l46. Inlet fluid will thus be available through approximately 270 or 70 percent of the peripheries and sides of both gears 82 and 84 thus essentially assuring that all gear teeth will be filled with and carry a full load of inlet fluid when they pass into sealing engagement with the arcuate surfaces 120 and 122 of thrust block 86, and the sealing surfaces of seal plates y88 and 90.

'Ihe seal plate area seals 94 and 96 are disposed in recesses 150 formed in the casing structure end plates 102 and 104 and lie within the area defined by the peripheries of seal plates 88 and 90. Seals 94 and 96 define the area in which pump discharge pressure, plus resilience of the seals, may act to Vforce seal plates 188 and 90 into a sealing relationship with the -faces of the gears 82 and 84 and the thrust block 86. There is an accurately controlled pressure force between the seal plates and the gear faces as well as between the thrust block and the peripheries of the gears and this accurately controlled force may be defined as being suiciently high in value to squeeze the oil film between the wear plates and the side faces of the gears and the thrust block to such a low value of .thickness that leakage between the sealing faces is at a minimum, yet not high enough in value so that the oil film is ruptured which would result in galling between the inner face surfaces of the wear plates 88 and 90 and the side faces of gears 82 and 84. This low value of film thickness is a desired optimum clearance and c-an also be defined as the least amount of clearance that can be tolerated from a lubrication standpoint and, therefore, the least clearance leakage that will result from pumping against a high discharge pressure.

Annular seal plate seals are resilient and have a crosssectional thickness greater than the depth of recesses 150. In the assembled pump the seal plates compress the annular seal plate seals a slight amount resulting in a mechanical bias urging the seal plates toward the side faces of the gears and the thrust block.

By the use of pressure controlled forces between `limited area contact members (the thrust block 86 and seal plates -88 Iand 90, the pump gears are pressure sealed in a definitive manner over a specific desired area which can be held to a minimum value. In contrast to a conventional fixed clearance gear tooth pump 20 which effects a pressure gradient seal over a Alarge area, the

4present invention provides a fixed, essentially constant clearance seal over a small area.

It will be clearly apparent that pumping action of the pump of this invention is not dependent upon the presence of a pump casing or closely fitting end plates as in the aforementioned fixed clearance gear tooth pump 20. Pumping action can be obtained with the pump components of the present invention without the necessity of an enclosing pump casing and end plates. This latter aspect is represented in FIGURE 8 where the casing is replaced by a skeleton support structure 152 which is necessary to journal the gears, provide a holding means for the thrust block and seal plates and enable a discharge connection. Such a pump can be immersed in the fluid Viding an effective direct pump inlet.

Casing structure 98 and end plates 102 and 104 in pump are required only as support for the gear shaft bearings and 112, to provide inlet yand discharge connections, and to maintain the annular and area sealing members 92, 94 and 96 in abutting and overlaying relationship with their respective components. In the majority of installations the casing will provide a physical protection against the danger linherent in rotating gears and efficiently channel the inlet fluid into the teeth on the gear peripheries.

With particular reference to FIGURE l, the seal plate 88, and the same is true of seal plate 90, is so formed to have a distinct radial clearance from the gear shafts 114 and 116. The seal plate 88 is also dimensioned to be disposed within matching recesses 152 and 153 in the casing structure 98 and end plates v102 and 104 respectively with substantial clearance between its edges and the edges of the recesses "152 and 153, within optimum limits to prevent its moving entirely out of desired p0- sition. Having such clearances, seal plates 88 and 90 will have complete freedom to float within optimum limits, the edges of recesses 152 and 153 keeping the seal plates from moving outside of the area for which sealing is desired. Actuall construction of the seral plates need not necessarily be the particular construction shown in FIGURES l, 2 and 3 but should utilize the floating principle. The term floating used hereinl and in the claims, in connection with the pump discharge seal components, i.e., the seal plates and the thrust block, is intended to mean that suc-h components may bodily shift their positions in more than one path relative to Veach other and to the pump gears, at least one of such paths being directed toward and away from the pump gears.

The area of seal plates 8S and 92 encompassed within the contines of area seal 94 and placed under discharge pressure is an area which is selectively defined to produce .a uniform loading between portions of the inner faces Operation In FIGURE l, tiuid will enter the inlet 1148 and pass into the gear recess cavity 146. Because 75% of the periphery of the pump gears 82 and 84 as well as approximately 70%of their side face areas are not confined in close critical relationship to the casing or the end plates, the inlet iiuid which is at relatively low pressure at 146 can enter the gear tooth cavities at many positions over an extensive area and at a relatively low flow rate which permits pump operation in the direction of the arrows (FIGURE l) at shaft speeds many times higher than conventional fixed clearance gear tooth pumps. The rotating gears pick up the inlet fluid in the spaces between teeth and carry such fluid toward the intermeshing gear position G. Progressing toward point G, the end faces of the gear teeth cooperate with a minute fluid film to provide a seal against the arcuate surfaces and 122 of the thrust block 86. Trapped liuid between gear -teeth cannot pass position G and cannot flow back past neueren@ 11 Arace 12s fofzthrust :block fas. :.Duevtofthe differential tarea `accurately designed between Vthefr'ontand re'arfacesfof 'thethlvust'bl'och 'the pressure diferential @forces urge 'the 'thrust'block S86 toward the 'gear peripherie's, this differential pressure being'suiiicient to squeeze the liquid betwee'n'ithe.arcuatethrust block surfaces 120 and 1.22 and ythe I' end faces ofthe gear teeth to a very thin film with laimi'nu'te' thickness value, yet not 'high enoughtorupture ythe-licpiidfllm. The Vmost etlicient fluid seal'is thus -prol'vided. i

Pressure on iiuid in pressure zone 126 will also communicate through the seal plate passages 134m the outer seial plate pressure areas `defined by the areaseals 94 to :thus provide the controlled differential pressure loading fontheseal plates resulting in a uniform loading `between ftheinner faces of the sealplates 8S and 99 and the side "faces of the gears 32 and 84 and the side faces of the thrust block 86.

Since only a very small portion 'of the periphery 'of the'pump gears 32 and 841, that portion of the gears Ybey'tween points lG andH in FIGURE l, is subjected to any `Vgradient of discharge pressure, the bearing loads which fresult from 'the unbalance between the discharge pressure fand the inlet pressure are substantially Vless than'those which occur in a fixed clearance `gear tooth pump. .These VE.hearing loads will be approximately of the bearing gloadslin `an equivalent size conventional pump, when the 5two pumps are operated at similar'capacity "and pressure.

For a'givensize pump gear (iLe. a gear with fspecificout- :side diameter and tooth-pitch) there is .a resulting maximum shaft diameter, which in turn fixes the maximum bearing size and capacity used'on such gear. Since the p'rojectedarea of suc-h gear (subject to pressure) is iixed 4by'c'onstiuction and the bearing load'capacity is fixed, it ffollows that the maximum unit pressure (hydraulic) under which a given pump is to be operated is also iixcd.

vReferring to FiGURE 9, it is immediately apparent that, since the projected area of the gears (which is su'ofjected to discharge pressure) is definitely limited by the laction of the thrust block and seal plates, a higher unit discharge pressure can be tolerated before the maximum Y allowable bearing load is reached, than will be possible in conventional pumps as in FGUITLES 5 larid 6. Con- `-versely, for equal discharge pressures, the bearing loads 4"wiil be but 60% or so of that of a conventional tixedclearance pump.

Again referring to FiGURE 9, the very much reduced areas over which the discharge pressure can act (in all -3 planes) materially reduces the weight of the cast pump 'leasing and end-plates. Additionally, the bolts which `are normally used toiasten the end-plates to the pumpfcasing can be a much smaller size.

The use of limited small areas of Contact `betweenthe Yinner-faces of the seal piates and the side faces of the gears as well as between the thrust biock'fand the periph- =era1 surfaces of twogear teeth permits delinitivc seal- By comparison pump mechanisms, exemplied bythe 4United States patent disclosures of Lauclr 2,527,941; Wichorek 2,691,945 and Lindberg 2,728,301, have'seal "plate surfaces incontact with 100% of the sidesurfaces "of the pump gears. As a result, pumps of such'construction show mechanical efficiencies in the order of %"to y%. In contrast to this, pumps using the principlesof this invention have been demonstrated to have mechanilcalv eciencies in the order of To achievethe necessary working clearances ina'n as- 'se'rnbled pump of the conventional, fixed-clearance type (as previously described) there are at least 22 dimenfsions, on component parts, which must beheld within yfvery close manufacturing limits. ThisV number is 're- A'duced to1l 'on the pump of this invention and may pos- -sibly be reducedstill further.

.' lock v'andfsealrplates is illustrated in iside wall of thrust block 86.

vThe-fcontrolledclearances,which are required for the optimum performance of the pump of this invention, are achievedlbytheabuttingand overlaying relationship ofthe vital components when under the'influence of controlled .'forces, which forces vare derived from and are proporl-tional .tothe discharge or working pressure of the pump. lThus,'thesefclearances are the result of 'component arrangement and fluid pressure.'forccs and are not Acreated by fthe painstaking and accurate fitting of components J(one with respect to the other) necessary in conventional nfixed clearance vgear pumps.

YFoi-'various Ymodifications of the principles of thisinvention,'reference will be had to FIGURES 10, 12-14 and 16-20. In FIGURE 10 the combination of thrust an exploded perspective. The vvseal plate 38 is illustrated with theafore- 'described high pressure passage 134 which diverts fluid from the pressure zone 126. However such fluid presls'ure passagecan be vrelocated Aas inthe seal plate `9tl '(FIGURE 10) 'which incorporates a passage 134 Y`disposed ladjacent 'an area Vof the thrust block 36' and coextensive with va luid passage 156 formed through lthe This is merely a different manner of providing fluid communication from the 'high pressurefluid to thearea deiined by the areaseal 94.

Unloading modification he'ipump of 'this invention is ideal for use in 'a circuit'where 'unloading of the pump is desired, such a circuitheingillustrated. in FIGURE 13. In unloading servicejitisdesirable tocause the pump to cease ldelivering pressureuidaftcr'a certain work cycle has been accomplished. [Thisis desired to conserve power and to avoidundueheating of the pumping iiuid. vOne such Vexample of an unloading system is in the use of a pump to power ahydraulic molding press 181 where fluid power.is requiredfora few seconds to close the pressbut no iluid power. is required while the press is held closed, for example, during a curing cycle of the work anticle beingsubjected to the press pressure.

Toutilize the pump 181i for such unloading operation,

lall components ofthe illustrated example may be essentially 'identical with that described for the pump embodiment 'Sil disclosed inFIGURES 1, 2 and 3 however in lieu 4of the relatively largeiiuid passages 134 through sealjplates 83 and 9), oriiice passages 182 are provided in seal plates 183 and 191i between the outlet pressure chamber and the area delined by area seals 1194. `It is to .be clearly understood that this unloading modification is equally applicable to Vpumps using any form of thrust block assembly such as the first, second and third alternate embodiments hereinafter described, and others contemplated Within the concepts of this invention. .The pump outlet is connected to a line 196, which includes check "valve 1% and connects to the pressure cylinder 1201i of hydraulic press 181. A by-pass line 202, which Yincludesa 'control valve 2114, connects betweenline 196 and a iluid reservoirl (not shown).

VTapped openings 2% and 208 in the pump end plates communicate with the area defined byarea seals 194 and enable conduit connections for lines 211B and 212 whichjoin in line'r214'communicating through acontrol valve 215 into the fluid reservoir.

To initiate system operation, both of the control valves fZMand '215 would be closed and pump'discharge pres- -'sure,comrnuncating .through the orifices `182, would be .present on the outer surfaces of seal plates 1% and in1the areas defined lby'the seal plate seals VY194. Under Ithis condition 'pump discharge atn full pressure Awouldjhe present in line 196 to be introduced in the pressure cylinderlilll When the press 181 is yfully closed andfull pressure is trapped in the press cylinder by the line check 'valve198 the control Valve 215 may be opened to drain into the fluid reservoir.

fDiiTerential pressure I thus created across the small Vni'ce 182 by a high volume drainage llow through valve charged through the pump discharge port because pumpi ing action is nulliiied by lifting of the Wear plates. Fluid is by'passed and can then only circulate with the gear within the pump casing.

When the control valve 215 is again closed, pressures on both sides of the seal plates will equalize and the compression of the area seals 194 (or a separate independent spring member not shown) will lforce theseal plates into sealing engagement against the gear side faces and the side faces of the thrust block, permitting differential sealing forces on the seal plates to provide selfcompensating high pressure sealing and pumping action is again initiated.

In connection with the use of this mechanism as a hydraulic motor, it should be noted that a motor .delivers power as a result of unbalance of forces about the gear shaftl centers.

Even though the hydraulic forces of the conventional xed clearance pump as shown in FIG- URES and 6 are very high the unbalance about the -gear shaft centers is not high.

In the improved pump of this invention the hydraulic forces are lower on the individual gear members but at the same time they are :unbalanced to a very high degree due to the fact that the hydraulic Iforces are localized through the coacting surfaces of the thrust block and gear teeth. This unbalance is what leads to a greatly increased torque output characteristic which will be present even at low shaft speeds in the present invention where the eciency .of

-the conventional Ifixed clearance gear teethmotors drops off considerably, even tothe point where the motor becomes inoperative- First alternate form of pressure seal A further alternate construction 220, illustrated in FIGURE 12, has a split thrust block 221 consisting of two similar blocks 222 and 224 resiliently biased. away from. each other by means such as a coil spring 226 disposed in seats 228. Such an installation permits'use of smaller areas on the thrust block under discharge pressure nlluence and permits separate floating andselfgaligning of the cooperating surfaces between each gear e and its associated half` of the thrust block assembly.

A variation of the split block embodiment is accomplished by removing a portion of the casing structure adjacent the rear portion of each thrust block halfv as indicated by recess 230 (FIGURE 12). In effect thisv arrangement provides a small elongate abutment area 232, the width of which can be minimized by beveling the corners 234, which will act as a hinge line enabling self-adjustment of the thrust block half for closer coaction between the thrust block arcuate surfaces and theend faces of the gear teeth. It is to be understood that a resultant component of uid pressures acting upon the seal portions against the gear teeth as they iirst come into sealing engagement with the block 212 than the unit pressure exerted against the teeth as they leave sealing engagemeut with bloclc 212. This relationship can be correlated with the oil lilm thickness versus unit pressure relationship, hereinafter discussed, so that an initial sealing pressure and engagement occurs between gears and thrust block assembly immediately adjacent the pressure dis- .jcharge zoneriandfa seating engagement-under:higher presa [sure-occursnear the' gear tooth. entrance portions ofthe thrust block arcuatesurfaces. This relationship will lead A. to a more eiicient seal because the hydraulic force tending to disruptthe seal near the entrance portion .of the thrust block arcuate surfaces would be greatly reduced and yet-would, be attempting to force a liquid iilm through a clearance of minimum value.

Second alternate form of pressure seal The pump embodiment 250 illustrated in FIGURES 16, 17 and 18 utilizes a full floating pressure discharge sealing means in accord with the concepts of this invention, the .primary difference being in the use of two thrust `block halves 252 which include a direct thrust block j to -pump body cooperation enabling the omission of a sepa- :ratearea sealmember.-

As shown in FIGURES 16 and 17, pump 250 has a body 254 wi th.endrcovers 255, inlet 256, gear cavity 258, gears260 and seal plates 262 similar to Ythose described 4inconneetion witlrthe pump in FIGURES l, 2 and. 3. Forclarit'y, the seal plate annular resilient seals are not shown and theseal plate 262 in FIGURE l6'is shown in yphantc'nn lines.

' l.Each side-of pump body `254 is recessed at264adjacent the ydischarge" side 'face' 266 of gear cavity 258, the dis- .charge side face 266, as illustrated being planar and paralv lel to a plane through the axes of gears 260. In this embodiment, the reduced pump body portion 268 between the recesses hasa critical thickness which is the same dimension as the width of the pumping gears.

'Two thrustblo'ck halves 252 of similar tapering shape are. disposed in sliding relation between the face 266 of `-reduced body portion 268 and the peripheries of gears 260. Compression coil springs 270 or other suitable expansible elastic devices, seated in opposed sockets 272 in the'inner faces 274 of the thrust block halves 252, maintain thetwo halves in an initial cooperative relationship -between gears 260 and body 254. The major extent of the contoured facev 276 of each thrust block half 252 (FIGURE18) is curved with a radius essentially equal .to that of gear 260'and the opposite face 278 is dat so -each block half 252 tits in the manner of a wedge between the flat body face 266and one gear 260 with the flat block lface 278 against the body -face 266 and the contoured block face 276 against the gear tooth periphery portions. A small portion of contoured face 276 at the narrow end of each thrust block half 252 is relieved by a short surface 280 (FIGURE 18), parallel to the flat face 278, permit- -ting unobstructed gearA tooth entry to the contoured face 27 6 of each thrust block half 252.

The thrust block halves 252 have a width dimension equal to that ofthe gears 260 and the reduced width body portion 268. The seal plates 262 are disposed in a planar sealedrelationship over the side faces of the gears 260, the

'thrust block halves 252 and reduced body portion 268 and are maintained in such relationship in a manner as described hereinbefore with respect to FIGURES 1, 2 and Pumped fluid enters the body inlet 256, is picked up by the gear teeth around the major portion of the periphery of gear cavity 258 and carried into the discharge pressure 274 and 276 of thrust block half 252 represent components of uid pressure acting on thrust block half 252 in a direction parallel to the discharge face 266 of the'body cavity 258. The force acting on thrust block face 274 is discharge fluid pressure whereas some of the lopposed components of force acting on contoured face 276 are dist charge pressures and some are fractions of discharge pres saure, :depending upon'the position :of ,thegeontactinggear :teeth and the effective fluid -fseal between .gear :teeth ,and the Acontoured face 276. It is cleanfromananalysis :of the rcomponents of force represented v in :FIGUR-,E 1 81 that :the .unbalance of forces (resultant ,R 1in ;-EIGURB -l;8) tending to forcei thelhalves 252:against1the; gear teeth, Vcan "beicontrolle'd `to va small value. {Ehemajorcomponents of force developed by the fluidiundergpressure ,on .reach thrust block half 252 Will .beacting tobias thethrust block halves 252 against the discharge face 266 o'f the body v"cavity '258 andare utilizedv to provideafdirectfcontact-seal -'(metal to metal vif the thrustrblocksand casingare both -made o-fmetal) :at plane A'(FIGURE'18) therebymbviat- Ving the need vfor the annularlip 'type seal member 920i `4:FIGURES 1, 2 an`d3. The desire'dresultantlforce Ris 'designedftoprovida as close'as possiblefaminimumthickness fluid lm seal between the contoured :faces .276 of thrust' block halves 252'and Vthergear teeth.

.'EIGURES; 19 and' zo'iuustratesathird alternative Vform f `'ofzi-the discharge thrust block pressure seal in a `pump $00 in which the floating thrust block302 andthe means providing its annular seal with the pump casing are com- .bined in a .unitary flexurahmemben In otheraspects, this embodiment'is. similar to that disclosed in FIGURES '1, 2 Land 3.

Although the, illustrated pump'j body 304-wi'tl1 its Y inlet .'30'6 yand discharge tting 308 are `fabricatedfrom several components, if desired, it couldbe made' integral withtwo end plates as in"FIGURES' 1,'2 and 13. 'The'two part ,pump body 304, with the V.main portion v3,10, A.containing theAgear cavity 312, and the. auxiliary side plate'314, fastened to the dischargeY side 'of body* portion'3101by pump ".bodyend plates and bolts'315, enables.v ease of '.assembly rof the thrust block' 302 andfrmly positions-the end portions 31'6 of thrust block 302'againstgshoulders"317.111 the major body portion'310 for a purpose to' be'laterjde fscribed. The discharge fitting 308 is threaded into Ya .sleever'gland'318, andhas .a spigotportion 13 20 which y projects through the sleeve gland. A11 annular recess-322v inthe face of sleeve gland i318 surrounding the spigot 320receives an O-ring seal' 324 of suitableresilient material such as Teon Sleeveugland 318 is'fastened to thepump body side plate 314 by screws 326 with the 'discharge fitting spigot 320 disposed in a dischargeopening 328 of a discharge passage through the pump bodynside plate 314. In assembly, the O-ring 324V is compressed to ahigh pressure fluid tight seal between the Ydischarge'tting 308, sleeve gland 318 and pump body side, plate 314.

Seal and wear plates 330 (FIGURB) are essentially identical to those illustrated in VFIGURES 1, 2 and'3,

iloatingly overlying a portion of the'side faces of gears 332 adjacent the dischargerportionof lthe gears, and the .major` extent of side facesofthe unitaryjthrustblock 302. V,Of course in all embodiments the seal-plates. utilize some form of upper resilient seal member as`94'jn'l-FIGURE 1 and have a pressure equalizing passage 1as.13,4 in LG- "URE 1 connecting both sides of the plate.

Flexural thrust block ,member,.302 isrrestrained be- "tween pump body members 310.and314.for accurate,

positioning ismade of a .wear resistan t,-yet exible, ma- ,.terial such as Micarta, .nylon, Teilon,etc.,has. a width the same as the width oftpumpgears ,332,.and is hollow withlan 'annular4 sealingllip .334 ,engagingV the;.inner .Q face 336 of pump body siden plate 314. .The face i338 of thrust block 302 whchfaces ,thefinteriorof pump;bo dy 304 is contoured to be in reasonably close proximity-to .the tips orperiphery ofthe gear ;teeth-when the pump has .zero discharge. pressure. w

. As pump discharge pressure increases, the'pumpedluid ,v

masses-,through a passage340 in; the vcentral portionrof `thrust block 302 enabling fluid discharge: communication throught pump body side plate 314 and-discharge-'tting l,308. Fluid under discharge pressure-acts onall..interior surfaces of'the, hollow Atiexural thrnst block *302,v forcing` "16 :the .sealinslpstinto a hie-h pressure Seal against -side nrlate .face `313.6 and preventing Vhigh 'pressure fud from Tescapiugfrorn .between the thrust .blockend pump body.

:Under pumped .nuid v.discharge pressure, as .denoted Lby .the-arrowsinFIGUlE 19, Y0,11 portionsofeenteured thrust block face338-and against the greater ,area ofthe opposed inside fthrust blockrsurface 342, a differentahforce R1 (FIGURE 19) is created on the thrustblock wall 344 in- Lducingbendingfingexuralthrust blockvmember 3 02 from its en ds 3,16 v,which engageithefpumtp body shoulders 317. The dellection'of thrust block wal1,34,4 due toa l,bending momentrRlxM (whereM, FIGURE 19, V is th,e,dist ance betweenrRl and-the outer edge ofthe A innerthrust block faeelZ) resultsinvarying degrees of deflection dueto the tapered cross :section Vofthrust-lslocl: -wall -344 and Such deflection will be highest adjacent the Adischarge opening 340, This deflection closes down thegaptbetween :gear peripheries andthe contoured face -338of the thrust block' 302 as discharge pressures increase, t thereby reducing leakage past the tips ofthe gear teeth.

ItfisgobviousthaL-by skillful and careful incorporation of y'design dimensions, Athe physical/,proportionsof ,thrust .block member 302can be so'determned-as to maintainfa Vconstant minimum fluid sealing .leakage (irrespective of discharge pressure) past the -gear tooth tips. .This condition :will beideal for low .Wear and long life.

'It was previously pointed Iout that ,:a discussion .would Vbe presented concerning frelationshipsbetween the uid vflow `and the clearance existing between-two relatively -movingcomponents in :which that -clearanceis-.usedto .effect'a iluid -seal and where. actual contact of -the relatively moving components is lnot desired.

:It is known that fon-a given pressure 'differential across :a slotthat the volume of fluidflow will vary in proportion to the cube of the clearance. Therefore,vthe,smaller the dimension of critical clearance or slot Width which can be obtained without causing a-rupture of the sealing uid ,lm the more positive sealing effect will result. A relationshipexists between the'unit pressures ontwo relativelymoving components tending to` force those componentsinto actual engagement and the dimension of uid film thickness betweenthe two components. This relationship can be determinedby laboratory test equipment and carefully correlated to the type of uid being used to obtain the Iiluid lseal between vthe relatively moving parts. In furtherance of-this belieffexperimentatio n 'is being carried out to determine the-relationship between Athicknesses of various uid films and the unit pressures applied thereonpfrovm some value closeto adifferential pressure up to a value-V at which the lm is ruptured. Presently available ,information indicates that the relationship Aof vfilm thicknessto unitpressure will approximate vthe ,curveshowd in 3 FIGURE 151 in .which the 5 iilm thickness g rapidly Vdecreases yto;,aI leveling y olf-position and at some finite valueindicatedby the pointjPfrof the curve will v abruptly break and he disrupted. vIn .accordance `with ,such theory, arange of unit pressures, for example the approximately; level portion-R of-FIGUREIS, can be :determined for a specificl uid being; pumped within which the resultant iluid lm thickness will-,be essentiallyat the minimum value which can beobtained prior to the point of rupture. Utilizing this knowledge the `design differenv,tial areasenabling Aa biasing hydraulic pressure to act on the thrustblock ofl this invention can 4be accurately controlled inaccord with specific conditions of pump'use, ,such as type of fluid and working pressure ranges, to vprovide this minimum thicknessjof .fluid between the end faces of the gear teeth and the arcuate thrust-block surfaces 'and 122 underpressures well below that required to rupture the film-and to .provide the most eiective fluid seal at thosepoints. This sameknowledge can 4be utilized in designing the diierential pressure areas of vthe -seal plates to thus obtain a safe unit-pressure which nevertheless enables the desired minimumthickness lof uidlm between the seal plates and the side faces-0f the mme@ gears and the Side .faces f the thrust block. .The ,tyre .ef optimum clearance pump herein before disclosed Ienables utilization of such knowledge to obtain a much higher efficiency gear tooth pump than any heretofore proposed.

The foregoing description and drawings disclose various constructions and principles of operation for a self compensating optimum clearance gear tooth type pump in which enmeshed gears are disposed with a sealed coaction against a floating thrust block, and two oating side seal and wear plates aredisposed with sealed coaction against `the pumping gears and thrust block. The pump casing and casing end plates are used to provide bearing support for the gears and back-up supportfor the floating thrust block and the Seal and wear plates and are not used to provide any direct sealing cooperation with the gears, hence no critical clearances between casing and pumping seal surfaces of relatively moving components are required. By utilizing floating ,thrust blocks and iloating seal and wear plates having sealed diiferential areas in communication with discharge duid under pressure, a controlled force biasingthe iloating components into `close fluid sealing engagement with portions of the pumping gears, is obtained. An adaptation of the floating sea-l and wear plates to control pumping output by selective relief of wear seal and plate biasing force is enabled by providing orice ,bleeds through the seal and wear plates.

The invention may be embodied in other specific 'forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicatednby 'rgears; seallng wear plates oatmgly sh1ftably disposed on the appended claims lrather than by the foregoing description, and all changes which come Withinthe meaningand range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1, A tooth-gear pump with self-energizing pump surface sealing including: discharge fluid actuated, shiftable, gear periphery sealing means; two separate spaced apart discharge uid actuated, floating, gear side surface sealing means in sealed combination with said gear periphery sealing means; and means mounting the tooth-gears, said periphery sealing means and said two side surface sealing means for -independent shifting of each of said three sealing means and independent floating dispOsition of at least said two side surface sealing meansrelativeto said periphery sealing means and the tooth-gears.

2. A gear pump comprising: support structure, meshed gears journalled in said support structure; outlet thrust block means, contoured to `tit in iiuid sealed engagement against adjacent end faces of the teeth of said gears, floatingly shiftably mounted in said support structure; and seal means riioatingly shiftably disposed in said support structure on each side of said meshed gears and thrust block means sealingly engaging adjacent surfaces of said gears and block means; said thrust block means and said seal means on each side being shiftable independently of each other.

3. A gear pump comprising: support structure; meshed gears journalled in said support structure; outlet thrust block means contoured .to t in lluid sealed engagement against adjacent end faces of the teeth of said gears and oatingly shiitablyl mounted in said support structure; means between said support structure and said outlet thrust bloc-k means to provide a bias force tending to urge said thrust block means against said gear end faces; seal means iloatingly shiftably disposed in said support structure on each side of said meshed gea-rs and thrust block means sealingly engaging adjacent surfaces of said gears and said thrust block means; said thrust block means iand said seal means on leach side beingpshiftable independently of each other; and means between each seal means and said support structure to providel a bias force tending to urge said seal means .against the gears .and said thrust blockmeans.

4. A Agear pump comprising: support structure; meshed gears of equal thickness journalled in said support structure; pump outlet thrust blo-:lr means having" side faces, a thickness yequal to that of said gears, and contoured to t and shiftably mounted in said support structure between and adjacent the end faces of teeth of said gears with said thrust block means side faces coplanar with the side faces of said gears; means between said support structure and said outlet thrust block means to provide a bias force tending to urge said thrust block means against gear teeth end faces; seal means floatingly, shiftably disposed in said support structure adjacent each side of said meshed gears and of said thrust block means sealingly cooperating with adjacent surfaces of said gears and thrust block means to provide a discharge pumping cavity; said thrust block means and said seal means on each side being shiftable independently of each other; and means between each seal means and said support structure to provide a bias force tending to urge said seal means evenly toward the gear side faces and the side faces of said thrust block means.

5. A gear tooth pump with self compensating optimum pumping sealing clearances comprising: a support structure; enmeshed toothed pump gears journalled for rotation in said pump structure; discharge thrust block means maintained by said support structure in shiftable disposition genera-lly between said pump gears adjacent their meshed teeth; means to exert a force on said discharge thrust block means tending to urge said thrust block means toward the end faces of the teeth of said pump each `side of said pump gears and said thrust block means and, in conjunction with pumped fluid, to provide a iluid seal overlying the pumping portion of said gears and the `space between the thrust block means and'said gears; said thrust block means `and. each of said sealing Wear plates being separate components; and means to create `a differential fluid pressure on each of said sealing Wear plates tending to bias them toward said gears and thrust block means.

6. A meshed gear tooth pump comprising: `a full floating discharge zone sealing assembly having iirst means with ya discharge passage therethrough and opposed differential areas subject to pumped uid under discharge pressure maintaining saidfrst means in self-compensated pressure sealing engagement with teeth faces of the gears adjacent the `meshed tooth discharge zone, and second v and thi-rd Imeans structurally separate from each other and from said first means and floatingly shiftably disposed respectively on opposite sides of the gears adjacent the meshed tooth discharge zone, each of said secondand third Qmeans including opposed differential `areas subject to pumped fluid under discharge pressure maintaining each of said second and third means independently in self-compensated pressure sealing engagement with said respective sides of the gears and with said first means to provide a meshed gear discharge chamber between the gears and said discharge passage, and each of said rst, second and third means being independently shiftable relative to each other. i

7. A meshed gear tooth pump as defined in claim 6, wherein at least one of said second and third means include an orifice bleed between their said opposed dijferential `areas and a selectively operable controllable fluid pressure relief means is provided in fluid communication lvvlithdth-emeshed tooth discharge Zone through said orilice 8. A meshed gear tooth pump as deiined in claimr6, whegein the meshed pump gears are equal in width; said first means includes a thrust block means, contoured to sealingly engage the teeth end faces of the gears -adjacent their meshing position, having a width equal to the width of said gears; `and each of said second and third means includes a seal plate in iluid sealed engagement with said gear side faces and said thrust block means with a fluid 19 passage through each plate from the meshed tooth discharge zone.

9. A meshed gear tooth pump as defined in claim 8, wherein means including an annular resilient seal provide a fluid tight variable volume chamber on the sides of each seal plate opposite the meshed tooth discharge zone, said fluid passage through at least one of said seal plates comprises a fluid balancing bleed, and a selectively operable Huid pressure controlled relief means is in fluid communication with said fiuid tight variable volume chamber of at least said one of said seal plates.

10. A meshed tooth pump as defined in claim 8, wherein said thrust block means constitutes at least two parts each of which is contoured to sealingly engage the faces of one of said pump gears adjacent the pump gear meshing position.

11. A meshed gear tooth pump as defined in claim 6 wherein the pump includes a casing structure journalling the pump gears, providing sealed support for said sealing assembly and having non-critical relative large clearances from gear surfaces particularly adjacent the gear teeth.

12. A meshed gear tooth pump as defined in claim 11, wherein the sealed support provided by said casing structure for said sealing assembly provides an isolated pump inlet chamber and outlet chamber and said casing structure has an inlet and discharge respectively leading to said inlet and outlet chamber.

13. A meshed gear toot-h pump as defined in claim 12, wherein the inlet chamber encompasses approximately seventy percent of each of the pump gears.

14. A gear tooth pump which has a casing support structure for intermeshing pumping gears with non-critical clearances between the casing support structure and the gear side faces and teeth peripheral faces, a thrust block shiftably mounted in said support structure and engaging a minimum portion of the gear peripheral faces, and two seal plates structurally separate from each other and from said thrust block and floatingly shiftably mounted in said support structure overlapping said gear side faces and said thrust block and each of which is sealingly biased by discharge fiuid from the wall of said casing into engagement with the gear side faces and the thrust block.

15. A gear tooth pump as defined in claim 14, wherein said seal plates which sealingly engage portions of the side faces of the gear teeth and the thrust block seal a space between said thrust block and intermeshed gear teeth in fiuid communication with the pressure discharge side of the pump gears, and an annular resilient seal structure disposed between each said seal plate and said casing aids in maintaining the seal plate against said gear and said thrust block,

16. A self-compensating gear tooth pump comprising: a support structure which journals the pumping gears in meshed relation; a thrust block shiftably disposed in said support structure, contoured to fit a portion of the peripheries of the pumping gears, having a thickness substantially exactly equal to the thickness of the pumping gears and having a discharge passage extending through said thrust block from the gear side pressure face of said block; a biasing means maintaining said thrust block in sealing engagement with said gears; a discharge pressure area provided on the outlet side of said thrust block pressure passage of sufficiently greater dimension than the effective area of the thrust block pressure face to provide a controlled biasing force on said thrust block; and side seal means overlapping said gear side faces and said thrust block, each side seal means being sealingly biased by discharge fluid from the support structure into engagement with the gear side faces and the thrust block, and each side seal means being oatingly shiftably disposed in said support structure independently of each other and of said thrust block.

17. A self-compensated gear tooth pump as defined in claim 16, wherein said side seal means includes two seal plates overlapping the sides of said thrust block and the faces of the teeth of intermeshed gears adjacent theirY discharge to completely cover the pressure discharge space between the intermeshed gears and said thrust block, and a resilient device cooperates between the seal plates and the support structure to bias the seal plates toward engagement with said thrust block and said pumping gears.

18. A self-compensated gear tooth pump as defined in claim 17, wherein said resilient devices are annular seal rings and means provide for passage of pumped fluid under pressure to the area on said seal plate defined by sai'd sealing ring so output pump pressure can be utilized to bias the seal plates toward said thrust block and pumping gears and the biasing force will be automatically compensated for changes in pump output.

l9. A self-compensated gear tooth pump as defined in claim 18, wherein said seal plates have an orifice type fiuid communication to the pump pressure space and means provide a control outlet from the seal plate sealed area selectively operable to completely relieve fiuid pressure from within the seal plates sealed area thus enabling the seal plates to be biased by pump output pressure out of operative sealed engagement with the thrust block and pumping gears to effectively by-pass pump discharge and cause immediate cessation of high pressure pumping output.

20. A meshed gear tooth pump as defined in claim 16 comprising a full fioating discharge zone sealing assembly providing self-compensated pressure sealing means in liquid lm sealing engagement with teeth faces of the gears adjacent the meshed tooth discharge zone and with opposite sides 0f the gears adjacent the meshed tooth discharge zone; said self-compensated pressure sealing means including said thrust block means and said side seal means, each of which have opposed differential control areas subjected to pump liquid under discharge pressure and being proportioned to provide a unit pressure differential force on each of such means in a sealing direction within a desired range of unit pressures which when applied to a film of the pump liquid, existing between said thrust block means and said gears and between said side seal means and said gears, provides an approximately minimum thickness film of the pumped fluid and the maximum pressure value in said range being sufficiently lower than the pressure required to rupture the film of liquid to normally assure no rupture of Said film during pump operation.

21. A gear pump comprising: support structure; meshed gears journalled in said support structure; outlet thrust block means comprising two tapered half blocks contoured to fit in fluid sealed engagement against adjacent end faces of the teeth of said gears and fioatingly shiftably mounted against a surface in said support structure opposite the end faces of said teeth; means between said half blocks to provide an initial bias force tending to wedge said thrust block halves between said gear end faces and said support structure surface; seal means fioatingly shiftably disposed in said support structure on each side of said meshed gears and thrust block means sealingly engaging adjacent side surfaces of said gears and said thrust block means; each of said seal means being independently shiftable relative to each other and to said thrust block means; and means between each seal means and said support structure to provide a bias force tending to urge said seal means against lthe side surfaces of said gears and said thrust block means.

22. A gear pump with self-compensating pump surface sealing comprising: a flexible differential area discharge fluid actuated gear tooth end face sealing and discharge passage means in sealed combination with two oating and spaced apart differential area discharge fiuid actuated gear side surface sealing means and support means mounting each of said means for shifting movement relative to and independent of each other.

' 23. In a gear tooth pump which has a casing support structure for intermeshing pumping gears with non-critical clearances between the casing support structure and thegear side faces and teeth peripheral faces; a flexible thrust block, with a discharge passage, engaging a minimum portion of the gear peripheral faces and including an annular flexible pump casing sealing lip surrounding the thrust block discharge passage; and two seal plates floatingly shiftably disposed within said casing support structure, overlapping said gear side faces and said thrust block and both seal plates being sealingly biased between the wall of said casing into fluid sealed engagement with the gear side faces and the thrust block; each of said block and said two seal plates being structurally separate components.

24. A self-compensating gear-tooth pump comprising: a casing structure which journals the pumping gears in meshed relation and includes an outlet; a flexible thrust block floatingly shiftably disposed in said casing, contured to fit a portion of the peripheries of the pumping gears, having a thickness substantially exactly equal to the thickness of the pumping gears, a discharge passage extending through said thrust block from the gear side of said block, an annular ilexible sealing lip on the outlet side of said thrust block engaging said casing around said outlet and maintained in sealed disposition against said casing by discharge pressure, and a discharge pressure area provided on the outlet side of said thrust block of sufficiently greater dimension than the effective area of fthe thrust block pressure face to provid-e a controlled biasing force deecting said thrust block into iiuid .film sealed relationship with the pumping gear teeth; two structurally separate seal plate means floatingly shiftably ldisposed within said casing structure, overlapping the side faces of said gears and at least the sides of the por tion of said thrust block which fits the peripheries of said gears; and means to create a differential fluid pressure on each of said seal plate means tending to urge said seal plate 'means evenly toward the gear side faces and said thrust block.

25'. in a gear pump, a casing, a pair of meshed gears journalled in said casing, a Huid inlet for said casing opening to an enlarged fluid pick up space at one side of said gears, an outlet for said casing, and means floatingly shiftably mounted in said casing disposed between and embracing said gears Iat their other side and extending between said other side of the meshed gears and said outlet yclosely confining the fluid picked up by said teeth substantially only on the sides and teeth faces of said gears adjacent said outlet and delivering said fluid to said outlet at materially increased pressure; said means in the `casing comprising a fluid throat defining means at the discharge side of the meshed gears and at least two side members urged by uid pressure developed within said casing into running seal engagement with the teeth sides and faces of said gears and the sides of said thro-at defining means, said throat defining means and each of said side members being structurally separate each from the others.

References Cited in the tile of this patent UNITED STATES PATENTS 164,147 Conver lune 8, 1875 2,105,259 Oshei Jan. 11, 1938 2,147,777 Oshei Feb. 21, 1939 2,420,622 Roth et al. May 13, 1947 2,622,534 Johnson Dec. 23, 1952 2,742,862 Banker Apr. 24, 1956 2,817,297 Mosbacher Dec. 24, 1957 2,824,524 Banker Feb. 25, 1958 2,845,873 Lapsley Aug. 5, 1958 2,855,854 Aspelin Oct. 14, 1958 FOREIGN PATENTS 158,367 Sweden Mar. 26, 1957 625,405 Germany Feb. 8, 1936 

